In a data processing system, system storage needs to be accessed frequently and thus, efficiently so that system performance is not degraded. Typically, before system storage is accessed, one or more controls associated with accessing the system storage are set. These controls include, for instance, manipulation of storage keys, commands for expanded storage and controls associated with addressing modes.
Previously, in architectural systems, such as International Business Machines Corporation System 390, in order to alter one of the storage controls associated with accessing system storage, a System 390 instruction, as one example, was used to load the program status word with the desired control information, perform the storage access and then reload the program status word with the previous control information. The loading and reloading of the program status word or other control registers is time consuming and a degradation of system performance. Thus, a need exists for a technique in which storage controls used in accessing system storage can be overridden in a flexible and efficient manner.
Based on the foregoing, a need exists for a method and system for controlling references to system storage which provide flexibility and do not require the replacement of existing values set for storage controls. In addition, a need exists for a method and system for controlling references to system storage which enhance system performance. A yet further need exists for a technique for issuing system requests which is also flexible and does not require the creation of a new instruction to satisfy each and every system request desired.